Focke Wulf Fw200-A Condor

[aleatorylamp]

Hello Folks,
Well, as it turns out, at the end this project will need an own thread, because there are a couple of things that need attention before a CFS1 upload can be undertaken:

1) - Flight Dynamics:
Although the FS98 .air file is quite good, it´s for FS98, so it doesn´t take advantage of CFS1´s supercharger capacity. It´s in the making, and there may be some issues regarding the power curve for the 720 Hp @ 2050 RPM BMW 132-G1 engines with their single-speed superchargers, that need tweaking.
Update:
It appears that max. speed was 226 mph (at S.L.? dunno...), and apparently the Maximum Manifold presure of 1.2 ATA was maintained upto 6000 ft. Doing it this way in the .air file, there are unwanted peaks of almost 250 mph at 6000 ft and 9000 ft, even reducing the 226 mph at S.L. to 221 mph.
However, using a "similar" criteria of maintaining 720 Hp instead of 1.2 ATA upto 6000 ft, then the peaks come down by 6 mph, but it is still 14 or 16 mph too high. So, it´s still on the drawing board...

2) - Virtual Cockpit:
AF99 didn´t have enough parts to make a virtual cockpit, so it wasn´t included for SF98. Given the good FS98 panel by Pegasus Design, this was a viable option. However, not so for CFS1, because with SCASM, a virtual cockpit can be made, and it will be a good idea to include one. It will most likely have to be a call in the usual position of the listing for VCockpits, to some extra parts placed at the end, similar to the Zeppelin Staaken SCASMing.

3) - Panel:
The Pegasus Design Panel is very good for FS98, but needs different instruments for CFS1. Also, I don´t know if it will be very useful having 2/3 of the cockpit shown - it makes the cross-hairs seem off centre. Hence, for CFS1, it may be more useful to have a complete and centred panel. As right hand side instruments are repeated, possibly nav. and com. instruments will be handy there. So, while I´m at it, I´m making the panel bitmap too. Here´s a screenshot of the provisional panel - still including the Beckwith gauge (dig Ivan´s new gauges!).

In consequence, this project can´t be a direct FS98 upload into CFS1, but a CFS1 adaptation, and will require a little work before it will see the light of day. I´m sure it´s better to do it better than to leave it go as it is...

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Folks,
Constantly on the lookout for more technical details regarding engines and performance of the early civilian version of this aeroplane, Fw200-A, I have slowly been able to complete the picture. It appears that what was given initially as top speed of 224-226 mph, is more likely to be a max. cruising speed, and that the real top speed was 245-250 mph, at 6000-9000 ft.

The early Fw200-B version had a somewhat more powerful engine - 850 Hp, for which more exact details are available.
What is interesting, is that by extrapolating information from here to the 720 Hp engined version, the results are very similar to the newly found data, and would actually confirm it.

So, the .air file I am working on at present is surprisingly nearer to the specified performance than I thought, which is good.
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
OK, fine! Propeller pitch angles then refer to each of the graph lines ranging from 15 to 65. Of course... Thank you!
For the moment, my Qbasic program is giving me the advance ratios from which I can read the prop efficiency then...

Before that, however, I´ll see about the Hurricane propeller tables though.
You do have quite an eye for things, don´t you? That´s included in the "empirical intuition"!

I ´ll let you know how it develops!
I was actually quite looking forward to some real butchering, but maybe it´s a better idea to try something not so gory first, just in case we can save ourselves all the hassle.

OK! I´ve put in the Hurricane´s table 512, and I´m completely speechless, flabbergasted, amazed...
A quick test reveals the following maximum speeds:
>at 300 ft, 226.6 mph, just 0.2 mph lower, and Hp is exactly 720!
>at 9800 ft, 241.3 mph, only 0.5 mph slower, and Hp is the same as it was - 654 Hp!
I´ll do the rest of the tests tomorrow, but it looks like we´ve got a winner here!

How on earth could you identify this just like that?
The Hurricane engine is 1030 Hp in CFS, and higher in reality on some versions...
How would that propeller so quickly appear to be so useful?

I´ll gladly do without the butchery! Here we´ll apply the law of minimum effort...
I´ll just adjust the Oswald factor ever so slightly to get S.L. speed up by 0.2 mph!

I still can´t believe it...
I ´ll celebrate with some Sweet Sherry for desert. To your health!!

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Just got back from Dinner and Grocery Shopping

Regarding how I picked the Hurricane Power Coefficient Table:
You are looking at the horsepower of the engines.
I suggest that you look at the formula for Power Coefficient instead.
Power Coefficient is basically a measure of how hard the propeller is to spin.
The Hurricane runs about 50% more power but also is swinging a larger propeller and is geared which makes the propeller easier to spin.
Another interesting note is that the actual Propeller rotational speed is nearly the same between the FW 200 and the Hurricane Mk.I.
(The propeller reduction gear ratio is 1.484)
When you are doing the calculations, don't worry about the Units of Measure too much because although it changes the number you get as output, you are just comparing numbers between different aeroplanes and the UOM cancel out.

I recommend that you adjust speed by a different method than Oswald Efficency.
That value is a modifier to the induced drag and at cruise and maximum speeds, induced drag is a VERY small component of total drag.
You will probably never see this in the FW 200, but increasing Oswald Efficiency numbers will increase the speed bleed in maneuvering and also have a much greater effect at low speeds.

Instead, I would suggest the following:
Drop the Airframe Drag slightly.
This number is very granular, so the effect will be probably more than you really wanted.
THEN, note the propeller pitch angle at maximum speed at Sea Level (328 feet).
226 MPH happens to be exactly 1.0 Advance Ratio, so if you adjust the Table 511 Efficiency down at that location, you should be quite close.

The reason I would do things this way is because in general, the Propeller Efficiency in the stock CFS Tables tends to be overly optimistic in my opinion and should be adjusted downward a bit if you have a reason. The efficiency also is a very finely adjustable value.

Let me know how things work and of course, please send me an updated version.

By the way, I will have a Soda, Tea or Coffee instead of Beer.
I was just commenting that typing is a terribly slow way to communicate compared to just having a conversation, especially if we had a simulator and a couple laptop computers and the Internet to find formulas and references.

With the Ki-61-Id, I already have some pretty good performance, but need to adjust how fast the propeller gains speed on take-off.
Right now, it conflicts with a flight test report.
There are a couple other aeroplanes that are affected (such as the Type Zero Mk.II fighters, so it makes sense for me to figure out a consistent method of generating propeller tables instead of hand editing them.

- Ivan.

[aleatorylamp]

Hello Ivan,
So, as promised, for purposes of comparison and possible exercises of deduction and/or extrapolation, I´ve managed to put together a small compilation of the different engines that were used on early versions of the Fw200, as well as a table with the preformance of the early aircraft models.

I have also included the results of the .air file with the manual Type-3 propeller, this time including RPM, Pitch and Thrust readings.

The fact that this 2-bladed propeller only had 2 manually adjusted positions, would indicate that RPM varies with throttle position and altitude. The propeller had no constant velocity governor.

Thus, I would be inclined to think that the behaviour of the model would now then be quite acceptable with the new .air file.
I wonder if you would perhaps also think so.

Thank you in advance for your opinion, but if it were too cumbersome or complicated to look at all this information, please only do so if you have the time and the gumption! I don´t want this to be a bother.

Even though the engine is specified at 720 hp max. power at 2050 RPM, effective RPM during flight varies:
In the model, at S.L. under full throttle, and also at different cruise speeds for different altitudes, RPM is 2028 RPM.
Then, highest RPM is 2170, and occurs at full Manifold Pressure Altitude.
The specified 2050 RPM only occur at 2500 ft and 19000 ft.

Despite the propeller being defined as Type 3, Manually adjustable, it is not really possible to manually adjust it other than to force a higher value upto the maximum limit set in the .air file - in this case 27.

What cannot be done in the sim is to maintain a low pitch, in this case the minimum value of 18. The sim will always select the optimum from what is available in the pitch range. You can see how the Beckwith Gauge displays what the sim is doing with the pitch angle. It is only at 18 at very low speeds, and immediately moves upwards to around 25 on take-off and shortly after, and continues going up with altitude. You can force a higher pitch, but it what for? You only lose power, so it doesn´t really make sense.

Also attached is the new .air file and a panel.config file including the Beckwith Gauge if it were to be necessary.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

We actually were out shopping most of the day and got back in the house only about two hours ago.
Hopefully I will have a chance to look at what you sent soon, but there are a few other tasks I am working on that I want to run for a while longer. I also need to help my Son in a couple programming assignments.

Regarding Propeller Pitch Ranges, Two-Pitch Propellers, and Constant Speed Propellers:
You say that you can get maximum speed and performance at about 27 - 28 Degrees, so why do you need coarser pitch?
Here is why and I have already asked about it a few times:
You get 720 HP at maximum boost and 2050 RPM.
You have given the boost pressure for Maximum Continuous, but what RPM is being used?

Consider what we know about Cars and their Engines. Airplanes have a lot of similarities.
In 1st Gear, I can get up to about 40 MPH.
2nd Gear can be run up to around 75 MPH or so.
3rd Gear goes well past 100 MPH.
This is at maximum acceleration.
Maximum Power is achieved at around 4400 RPM but fuel consumption is pretty high at this engine speed.
So what do we need more than three gears for?

....Because from a practical standpoint, much more time is spent under cruising conditions on the highway and
Not that much time is spent drag racing from a stoplight. (Take-Off and Climb)
On the highway in 5th Gear, I am typically running just a bit under 1500 RPM at 60 MPH and even with a big engine, fuel economy is not all that bad. (Cruise conditions)

With aeroplanes, there are a lot of similarities:
At Cruise we would have:
1. Low Throttle settings
2. Low RPM
3. Propeller in Coarse Pitch (High / Overdrive Gear)

....so it does help to have a higher gear / pitch setting even if it is only for cruise conditions.

- Ivan.

[aleatorylamp]

Hello Ivan,
I hope so much effort searching for a good college will bear the desired fruit, and that your son is recovering nicely!

Here, the holidays are being quite relaxing and good for a change, with some warmer weather and sunshine included. Today we had a healthy 2-hour walk through the forest in the mountains, and one daughter was at the beach with friends, and tomorrow there´s a barbecue at a friend´s vegetable patch in another forest in some other mountains, and the other daughter is going to the beach with some other friends! Then, on Sunday morning we´re all going to look for Easter-Eggs in the living room.

On Saturday I´ll probably get some more time for re-fine-tuning the Condor with the more realistic but less efficient propellers.
In order to get the objectives a bit clearer, at the moment I´m compiling a little comparison text document/chart showing the early Fw200 Condor versions and their engines and propellers, for comparison purposes. I´m just adding some imperial measurements to the metric information on the chart, and I´ll try to post it tomorrow.

It might help to illustrate the difference between the first 720 Hp engined proptotyes with their 2-position, 2-bladed manual propellers, and the subsequent short pre-production run and their 800 Hp engines with 3-bladed CV props.
Maybe I can clarify some doubts derived from a lot of confusing, often generalized information.
QBasic sound interesting as it is notorious for its mathematical capacity, so I´ll see what I can do!

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
I hadn´t exported any of the stock AC propeller tables yet, so I looked at a few points on the P51d graph lines just now, and they don´t have so many decimals at all! - two or three mostly, and the zeros don´show in the little AAM number window.

The Condor´s 511 Table I exported as a text file and posted a screenshot of, was the "two-graph" table I had made.
Typing the values from one graph to the other using the little number-window would have been endless, so I did it by moving the mouse, keeping the right mouse-button pressed, to adjust each point along each graph lline.

Much faster to do, but very slightly inaccurate. Visually the 2 graphs seem one line each, but in reality there are minor inaccuracies, which is the reason for the 15 non-zero digits in the decimal places!

I´m sorry if this has been confusing...

Cheers,
Aleatorylamp.

[aleatorylamp]

Hello Folks,
The panel for the Condor now has its set of engine gauges comnpleted with metric oil temperature and pressure and EGT/CHT gauges. The gauges are originally the default FSFS Cessna oil and Cessna egt-cht ones, but with a metric scale and German working on the dials. The panel in general follows the layout of the original airplane for the pilot´s position, and on the right, for the moment at least, is a functional radio operator/navigator´s position. Here´s a screenshot.
Any suggestions will as always be very welcome!
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Folks,
After extensively testing four or five different parameter combinations in the flight model, I´ve arrived at (in my humble opinion) very satisfying results, where the aeroplane´s specifications compare quite well to the performance of the model.

FW200-A Condor Specifications:
-------------------------------
Engines: BMW 132-G1 9 cyl Radials
Max. Power: 720 hp @ 2050 RPM (5 min.)
Cont. Power: 550PS at 1930 RPM

Full 1.2 ATA altitude: 5905 ft
Specific Fuel consumption: 230g/PSh
I haven´t tested this, and for the moment, there´s no gauge except Mr. Beckwith´s stack.

Ceiling: 19000 ft (because of max. possible altitude without pressurized cabin).
Max. Speed: 226 mph at S.L.
Max. Speed: 242 mph at 6000-9000 ft
Cruise: 208 mph at 3280 ft.
Cruise: 217 mph at 12467 ft
Eco cruise: 197 mph n.a. ft.

Flight Model performance:
-------------------------
Max Speeds:
-----------
SL.300ft:226.4 mph, 720 hp, 34.9 MP (1,2 ATA)
6000 ft: 242.4 mph, 754 hp, 34.7 MP (1.2 ATA)
9000 ft: 241.8 mph, 674 hp, 31.1 MP (1,03 ATA)
12500ft: 239.7 mph, 582 hp, 27.0 MP (0.94 ATA)
15000ft: 239.6 mph, 521 hp, 24.4 MP (0.85 ATA)
19000ft: 237.0 mph, 435 hp, 20.7 MP (0.72 ATA)

Cruise Speeds:
--------------
The model´s cruise speeds compared to the specifications from the Pilot´s manual, occur at slightly different Manifold Pressures.

S.L. 328 ft:
Cruise spd. Spec: 201 mph, 0,98 ATA. - Model: 0.9 ATA
Eco-Cruise. Spec: 186 mph, 0,74 ATA. - Model: 0,77 ATA
3280 ft:
Cruise spd. Spec: 197 mph, 0,94 ATA. - Model: 0,78 ATA
Eco-Cruise. Spec: 186 mph, 0,89 ATA. - Model: 0,70 ATA
9800 ft:
Cruise spd. Spec: 191 mph, 0,72 ATA. - Model: 0,61 ATA
12500 ft:
Cruise spd. Spec: 217 mph, n.a. ATA. - Model: 0,74 ATA

I would say the .air file is OK like this. Any comments will of course be appreciated and very well taken into account!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

What is the RPM you are using for maximum power and how much lower is the RPM for your cruise setting?
I suspect that might be the reason your throttle settings need to be reduced to match.

- Ivan.

[aleatorylamp]

Hello Ivan,
OK, how about some green tea then?
So, the set of numbers in the bigger Hurricane engine plus prop with gearbox, serve for the Condor. A nice surprise.

Ok, I ´ll have a look and see if I can follow your instructions to get that tiny edge of an performance increase out. Sounds like a piece of cake! An interesting way to finely adjust the speed.

I´ll let you know how it goes. Thanks very much!

Update:
OK! It´s almost perfect.
I lowered Zero lift Drag by 1 AirEd unit, and then went for Prop Efficiency Table 511.
At the first try I raised Pitch angle 35 graph to 1, smoothening out the surrounding ones, but performance rose by 4 or 5 mph, which was too much. Possibly I could have increased Zero Lift Drag by another unit, but I didn´t try.

Then I cancelled the first changes and this time raised the graph only very slightly, from 0.89 to 0.91, smoothening out the surrounding ones again, and the result is almost perfect. I just have to make some even smaller adjustments to get S.L. max speed down by only 0.3 or 0.4 mph now, and then check at higher altitudes. I´ll post the .air file when I´m done.
Thank you very much again!

Update 2:
It´s very interesting to see how this propeller efficiency issue works.
So, if I´m right, for a Maximum Speed adjustments, once you know the pitch angle from the Beckwith gauge, you go to the corresponding pitch angle graph and adjust the crest. Then, for Cruise Speed adjustments, after getting pitch angle, you use the formula to calculate the advance ratio, and obtain the point on the corresponding pitch angle graph to adjust that one.

Now I´ll see how it works out with the cruise speeds.

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Green Tea will work, but if I drink a lot of it, it should be decaf.

The big EEEEEEK is because of how you interpreted my instructions.

Hopefully the reasoning described below makes sense.
With the new Hurricane Mk.I Power Coefficient Table, you are close.
VERY close.
Performance is slightly under and with the really great mechanics we have, should be slightly Higher, not Lower than specifications (unless there is a reason why it should not be).

So, the first step is to Drop the Zero Lift Drag.
That should raise the speed by a couple MPH and if this were my project, I would leave it there.

Since you are trying to be more exact, the next step would be slow the aeroplane back down.
Reducing Thrust would do that,
so you want to slightly REDUCE efficiency where it matters in Table 511.
So going from 0.89 to 0.91 makes no sense.
It should go DOWN, not UP!
These are Double Precision floating point, so the adjustments can be VERY fine.

Where should the adjustments be made?
From what you posted earlier, the Sea Level speed was closer or less below the target than speed at altitude.
That means when you change the Coefficient of Drag, you would probably need to bring the SL speed down more than altitude speed.

Here you got lucky.
With this Engine / Propeller, your SL speed is at 226 MPH which is exactly Advance Ratio 1.00.
This would affect altitude speed also but less.
If you are trying to adjust altitude speed more, go for Advance Ratio 1.20 instead.

- Ivan.

[aleatorylamp]

Hello Ivan,
The Easter Bunny has just hidden the chocolate eggs - without breaking anything this time - and even though we are all grown-ups here, in a while we´ll be hunting. My wife says it´s childish and wants to stop the family tradition, but meets with stalwart opposition every year!

Thank you for your reasoning!

So, if we were to imagine a 2-gear car, High Gear would obviously be for Cruise with Overdrive.
The problematic choice for Low Gear would be between midspeed-accelleration and get-away-from-stop-light accelleration.
Given that not all landing fields were very long at the time, although the plane was specifically designed for Tarmac, they apparently only used Low for Take-off. Hence, the two real pitch settings may well have been 15 and 28.7.

However, the sim won´t allow fixing any pitch anyway except maximum full coarse, so one may as well use the CV option!

I should really do the RPM-Pitch-Thrust test on the CV prop .air file, if only just to see exactly what happens.
Maybe I should also look at the fuel flow reading for both .air files...
...the more you get to know, the more you need to know.

Strangely enough, the engine delivers more Horsepower with the present 18-27 "manual" setting, that with the 15-65 CV one(even if it doesn´t really work as "manual"), or maybe it isn´t so strange...

Cheers, and a very Happy Easter to all!
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

Happy Easter.

Remember what I was telling you about how screwed up the Propeller Efficiency Tables are?
It sounds to me like you are getting an unintended interaction between the places in the Propeller Power Coefficient Table and Efficiency Table just like I was describing. If you look carefully, you can probably find a propeller pitch limit that will let you get onto the perpetual motion roller coaster.
That kind of silly behaviour is why I will get back to working programs for Propeller Table Generation when I get past this texturing exercise I am currently on.

- Ivan.

[aleatorylamp]

Hello Ivan,
Thanks very much for your comment.
The revs stay on 2046 RPM all the time... I think we had this before on other engines.
For cruise speeds, e.g. 72% throttle or even 60% or 50% throttle has to be set, but RPM always goes back to 2046 or 2045 RPM.
This would be because of the C.V. propeller, I suppose?
Can this be corrected? At cruise it should really go down to 1930 RPM or so.
Possibly we are talking about having to use high and low manually set propeller pitches that these early Fw200-A units had. I just found out about that yesterday, going through all the pilot´s manual I had in the FS2002 version of the plane that I finally dug up from an old hard disk.

The better performing BMW 132 L and H versions of the same engine were installed on the FW200-A later, for the Fw-200S (previously an A unit) and for the Fw200-A0 series. One of the differences was that 800 Hp could be wrung out of them for 1 minute and for 5 minutes, but mainly it was the CV propeller. Early A units with the previous BMW 132-G1 engines had props with only 2 pitch settings: high and low angles. I would expect that this made a greater difference than the 80 hp take-off power increase.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
Thanks for your helpful comments. So I can improve it even more now!

Following your instructions, I had put the larger Propeller diameter back in. This needed a reduction in Zero Lift Drag, so I reduced it by one point, from 58 to 57. It was not completely enough to compensate for the larger propeller, and required a very slight increase in Prop efficiency.

Had I made a greater Drag reduction, I would have noticed that Prop Efficiency had to be corrected in the opposite direction!

S.L. Performance is now only 0.3 mph fast, and higher up it´s about 0.5 mph faster, all quite OK.
Cruise speed manifold pressure settings have also improved slightly compared to the ones from the pilot´s manual. The differences are a little smaller, so that has also improved.

But: It seems that it can be improved further, by reducing Zero Lift Drag a little more... perhaps by two or three points, so then of course, propeller efficiency will need to be reduced instead of increased, and the Manifold Pressure settings for Cruise speeds will fall into place!

Which is what I will do after another cup of tea!

As always, thank you very much... This is all very interesting.
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I get the misunderstanding now. I was figuring that you would keep reducing the Zero Lift Drag until you got a speed increase over the amount you needed.

The reason I choose this method is that from a realism standpoint, 0.89 is a pretty high Propeller Efficiency.
I would hope to see something in the 0.80 to 0.85 at Maximum Speed.
Now keep in mind that this is just from a bit of reading and a bit of experimenting with AIR files so if you want to do things differently, you own the project.

The problems I am trying to address with my own projects are that the Propeller Pitch Range is limited to around 23-53 Degrees.
The high speed range of cruise to maximum level speed are more or less correct, but the propeller is lugging at the low "maneuvering" speeds and not getting off the low pitch value and not generating the amount of thrust (efficiency) that I would want.
This is with the A6M3 Model 22 and A6M5 Model 52 Type Zero Carrier Fighters.
That is also why I never continued the path and released a A6M3 Model 32 version.
The flight model just didn't quite do what I wanted and I didn't have a means of correcting it.
It is also a problem with the A6M2 Model 21b, but is less noticeable because the propeller pitch range was different with the engines on the "Mark I" fighters.
The Zeros were known for having quite excellent low speed acceleration which meant that they could restore energy lost to maneuvering very quickly. Since I cannot do that, I compensate a bit by reducing the energy lost in maneuvering by having an Oswald Efficiency number that is a bit lower than it should be.

With the Ki-61-Id, the flight test mentioned that the propeller came off the low speed stop at a bit over 100 MPH just after take-off. Mine is about 20-30 MPH too high which bothers me, but makes no real difference from a performance standpoint other than making the acceleration a little too low at the end of the take-off run.
The reason I chose the Ki-61 to do the experiments on is that it is a simpler problem overall with much less in the way of cascading effects.
This is not to say that the flight model is correct; It just happen to be about where I want it to be.

Thus I need to be able to tune just a part of the Power Coefficient Table and as long as I am doing that, I might as well be able to generate the whole curve instead of just knowing specifically where to poke to get the effects I am looking for. Smoother curves are better.

- Ivan.

[aleatorylamp]

Hello Ivan,
How funny... Both funny "ha ha!", and also funny "strange".

Maybe they made the Propeller Efficiency Tables with a computer whose CPU had a faulty Mathematical co-processor.

I still can´t fully undestand all this - too many graphs on too many tables.
As soon as I try and relate the two to see the interaction I literally get a bit dizzy.

Anyway, I´ll decide what to do at some point. The manual prop setting does seem to be quite pointless though...

BTW, I tried a CV prop with Pitch range of 0 to 100, and I saw good accelleration at zero degrees pitch because the sim has a different calculation for low speeds. (As Beckwith explains,: "At speeds above the low speed theory limit, FS calculates thrust using propeller efficiency, engine power,and aircraft velocity..."). Then, I observed that at lift-off pitch was about 17, so maybe one should lower the minimum to 17...

Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I do not believe that the folks creating the flight models actually understood many of the capabilities designed into the system and that is why the flight models are as poor as they are.
I do not believe a Math Coprocessor was involved or even necessary for this kind of work.
My own calculation thus far are quite simple but then again I am not anywhere near finished yet.

My own belief is that the two pitch propeller is a workable possibility but I can't give you any useful advice at the moment because I have not experimented there yet. The constant speed propeller appears to be the more difficult but also more generally useful problem and I am working on that part first.
I have a few guesses on how to do the two pitch propeller which involve creating a very strange looking Propeller Power Coefficient table, but do not yet have the programs even to do the constant speed version yet. Basically it will look a lot like a horribly mangled constant speed Power Coefficient Table....

My technicians will be working on adjusting the spray guns at the moment to see what works best for doing a camouflage pattern for the Ki 61 Hien (which also is the main propeller test aeroplane).
See the attached screenshot for the un camouflaged aeroplane.

- Ivan.

[aleatorylamp]

Hello Smilo,
Thanks for your comment! So it´s not only me! Or my computer itself...
Sometimes when a post gets longish and I remember to safeguard myself just in case, I save it to the notepad, and if it disappears, I can retrieve it with the paste option.
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
It´s nerve wracking sometimes.
For the umpteenth time I had put in the ungeared propeller, but the gearing always managed to creep in again because of the 4 different .air files I was gauging against each other. It was also only very recently that I found out that the BMW 132 G1 had ungeared propellers, slightly smaller, and that subsequent versions of this engine all had geared ones that were a bit larger!

Update:
The whole engine seemed screwed up, but even the torque won´t need to be adjusted!
What I noticed was that RPM take longer to build up, so it was a matter of minimum propeller pitch, that had to be less.
For the moment, it seems to be getting fixed by lowering the minimum pitch from 23 degrees to 15.
Then, for higher altitudes, I think I may reduce the 65 degrees to about 50, and we´ll see what happens.

What a mess.... but it´s now less messy after the initial shock!
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp,

I think we have had this discussion a few times before and I THOUGHT you understood what I was trying to explain.
1. Set Engine Power with a constant speed propeller and whatever gearing it takes for your engine to reach full RPM.
Easy ways to handle this are to either change the gear ratio or the propeller diameter.
Consider this the Bench Tuning for the engine.
2. Set the Gear Ratio, Propeller Diameter and Propeller Pitch Range.
This is the reality part. The numbers are what they are.
3. Use the Propeller Power Coefficient Table (Record 512) to adjust the RPM response of the engine.

Building a Record 512 is a bit of a pain. I am actually trying to do some programming / spreadsheets to help create this table.
If you don't know how to do it (I still fall into this category), then pick a matching propeller table based on the power coefficient of the stock aircraft that best matches your particular aeroplane.

I currently have a project that needs this kind of work (Kawasaki Ki-61-Id) and a proposed project (Ki-43-I Hayabusa) that will depend on altered 512 Tables to behave properly.

If you can't get there, you can do as I have done and delay the release of the project or an alternative method which might help is to adjust the Propeller Diameter until things behave properly. I don't like that idea myself but am willing to wait until I have properly addressed the problem.
Being able to finish a project is my incentive for addressing the problem.

The bottom line is that tuning engine power really does not address the problem you are encountering.

- Ivan.

[aleatorylamp]

Hello Ivan,
From what you are describing about the models you are working on, some behaviour details seem to be more difficult to reproduce on the sim model than others. Then it is all the more gratifying when something specific does work! The details you are working on seem to be very specific and quite complicated. Good luck!

Usually I don´t find so many details available for the older models I work with, and something similar is happening with the Fw200. The maximum speeds are falling in place very well, but strangely enough, they were better with my slightly increased Prop Efficiency and less reduced Airframe Drag, than with the last tests after reducing Airframe Drag further, and also reducing Prop Efficiency a little.

Sea-Level speeds ended up a few mph on the high side, and at altitude there were only very marginal increases of 0.5 or 0.2 mph, but I think I have discovered why.

Strangely enough, the specific Manifold Pressure details for the three or four cruise speeds mentioned in the pilot´s manual just wouldn´t fit in correctly, but I deduced why - it´s a really stupid thing: They come from the documentation referring to one of the units of the Fw200-A0 limited production run, which were built while the first 3 initial prototypes were still being tested, and some of these fitted the 800 hp BMW 132-H or -L engines!

So obviously the 720 Hp engines on the prototype machine that flew the Berlin-New York record flight need different manifold pressure settings for said cruising speeds! That took a while to sink in... so I can discard that information. The lower Hp would also account for why it´s not working to increase altitude performance.

So it seems that the air file with the first modification of Table 511 after incorporating the Hurricane´s table 512 is more correct.
Anyway, it´s very pleasing how this is all turning out thanks to your indefatigable counselling!

I´m just preparing the new spec sheet for the performance of the new ungeared, 9.7 ft propeller engine, and I´ll post the new .air file. BTW, you are right about the 0.89 efficiency being too high for advance-ratio 1. It´s at 0.8585 - the 0.89 come from a higher pitch angle graph peak to the right! When I was adjusting the peaks at first, it wasn´t all that clear to me where I was. Sorry!

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
Yes, sorry! A short while later I remembered the discussion, and I realized what was causing the MP differences I was getting at different cruise speeds, compared to spec MP. But, I´m afraid I´m not about to fiddle around with the 512 propeller table entries.
I remember trying once or twice and only making things worse!

I found the P38 prop tables work better with the Do17-z2 and the FW200A. Then, the P51d tables did better for the Baltimores, as the props were considerably larger.

Before, I had 2.088 gear ratio (of the P51d), and 10.5 for the prop diameter, but of course, it is different now with the ungeared, 9.7 ft prop. The gearing seems to have a greater effect in this case.

I did the engine bench tuning and last night I managed to get the RPM correct again, and also had to lower zero lift drag for correct S.L. performance. Now of course, higher up it´s different, and it looks like the discrepancy with the cruise speed throttle settings is going to get worse.

So... Thank you very much for reminding me about playing with gear ratio and prop diameter as a get-by alternative to altering table 512 - I ´ll see how it goes.

Cheers,
Aleatorylamp.